Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/14—Macromolecular materials
  • A61L27/18—Macromolecular materials obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/14—Macromolecular materials
  • A61L27/26—Mixtures of macromolecular compounds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/12—Chemical modification
  • C08J7/123—Treatment by wave energy or particle radiation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/32—Joints for the hip
  • A61F2/36—Femoral heads ; Femoral endoprostheses
  • A61F2/3662—Femoral shafts
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/38—Joints for elbows or knees
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2400/00—Materials characterised by their function or physical properties
  • A61L2400/18—Modification of implant surfaces in order to improve biocompatibility, cell growth, fixation of biomolecules, e.g. plasma treatment
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2430/00—Materials or treatment for tissue regeneration
  • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2371/00—Characterised by the use of polyethers obtained by reactions forming an ether link in the main chain; Derivatives of such polymers
  • C08J2371/08—Polyethers derived from hydroxy compounds or from their metallic derivatives
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
  • G01B5/28—Measuring arrangements characterised by the use of mechanical techniques for measuring roughness or irregularity of surfaces
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces

Definitions

• This invention relates to a medical implant and particularly, although not exclusively, relates to an orthopaedic implant comprising a polymeric material, for example polyetheretherketone (PEEK).
• PEEK polyetheretherketone
• orthopaedic implants which comprise polymeric materials, such as PEEK
• PEEK polymeric materials
• US2010/0312348A Howmedica discloses an orthopaedic polyaryletherketone (PAEK) on polymer bearing and proposes a PEEK-based femoral head.
• PAEK orthopaedic polyaryletherketone
• PMMA polymethylmethacrylate
• the PMMA may be arranged in the femur and a femoral component of the hip implant may be positioned in the PMMA.
• PMMA is often referred to as a cement, it is more properly referred to as a grout which forms a micro-interlock between interstices in cancellous bone and in grooves formed in the femoral component of the implant itself.
• an interlock alone between the femoral component and PMMA may be insufficient in some cases.
• an orthopaedic implant comprising a surface arranged to contact bone in a human or animal body, wherein said surface of said implant comprises a polymeric material which includes a repeat unit of general formula
• said surface is a plasma treated surface.
• Said polymeric material may include at least 80 wt%, preferably at least 90 wt%, more preferably at least 95 wt%, especially at least 99 wt% of repeat units of formula I.
• Said polymeric material suitably includes at least 90 mol%, preferably at least 95 mol%, more preferably at least 99 mol % of repeat units of formula I.
• Said polymeric material preferably consists essentially of a repeat unit of formula I.
• said polymeric material is polyetheretherketone.
• Said polymeric material may have a Notched Izod Impact Strength (specimen 80mm x 10mm x 4mm with a cut 0.25mm notch (Type A), tested at 23°C, in accordance with ISO180) of at least 4KJm “2 , preferably at least 5KJm "2 , more preferably at least 6KJm “2 .
• Said Notched Izod Impact Strength measured as aforesaid, may be less than 10KJm "2 , suitably less than 8KJm "2 .
• the Notched Izod Impact Strength, measured as aforesaid may be at least 3KJm "2 , suitably at least 4KJm "2 , preferably at least 5KJm "2 .
• Said impact strength may be less than 50 KJm "2 , suitably less than 30KJm "2 .
• Said polymeric material suitably has a melt viscosity (MV) of at least 0.06 kNsm “2 , preferably has a MV of at least 0.09 kNsm “2 , more preferably at least 0.12 kNsm “2 , especially at least 0.15 kNsm “2 .
• the MV may be at least 0.35 kNsm "2 and especially at least 0.40 kNsm "2
• An MV of 0.45 kNsm "2 has been found to be particularly advantageous.
• MV is suitably measured using capillary rheometry operating at 400°C at a shear rate of 1000s "1 using a circular cross-section tungsten carbide die, 0.5mm (capillary diameter) x 3.175mm (capillary length).
• Said polymeric material may have a MV of less than 1 .00 kNsm "2 , preferably less than 0.5 kNsm "2 .
• Said polymeric material may have a MV in the range 0.09 to 0.5 kNsm “2 , preferably in the range 0.14 to 0.5 kNsm “2 , more preferably in the range 0.4 to 0.5 kNsm “2 .
• Said polymeric material may have a tensile strength, measured in accordance with IS0527 (specimen type 1 b) tested at 23°C at a rate of 50mm/minute of at least 20 MPa, preferably at least 60 MPa, more preferably at least 80 MPa. The tensile strength is preferably in the range 80-1 10 MPa, more preferably in the range 80-100 MPa.
• Said polymeric material may have a flexural strength, measured in accordance with IS0178 (80mm x 10mm x 4mm specimen, tested in three-point-bend at 23°C at a rate of 2mm/minute) of at least 50 MPa, preferably at least 100 MPa, more preferably at least 145 MPa.
• the flexural strength is preferably in the range 145-180MPa, more preferably in the range 145-164 MPa.
• Said polymeric material may have a flexural modulus, measured in accordance with IS0178 (80mm x 10mm x 4mm specimen, tested in three-point-bend at 23°C at a rate of 2mm/minute) of at least 1 GPa, suitably at least 2 GPa, preferably at least 3 GPa, more preferably at least 3.5 GPa.
• the flexural modulus is preferably in the range 3.5-4.5 GPa, more preferably in the range 3.5-4.1 GPa.
• Said polymeric material may be amorphous or semi-crystalline. It is preferably crystallisable. It is preferably semi-crystalline.
• the level and extent of crystallinity in a polymer is preferably measured by wide angle X-ray diffraction (also referred to as Wide Angle X-ray Scattering or WAXS), for example as described by Blundell and Osborn (Polymer 24, 953, 1983).
• WAXS Wide Angle X-ray Scattering
• crystallinity may be assessed by Differential Scanning Calorimetry (DSC).
• the level of crystallinity of said polymeric material may be at least 1 %, suitably at least 3%, preferably at least 5% and more preferably at least 10%. In especially preferred embodiments, the crystallinity may be greater than 25%. It may be less than 50% or less than 40%.
• the main peak of the melting endotherm (Tm) of said polymeric material (if crystalline) may be at least 300°C.
• a surface of said polymeric material has been plasma treated as described may be confirmed by use of ESCA - for example the surface of the polymeric material may have an increase in the number of oxygen groups.
• the contact angle with water at the surface may be reduced compared to an equivalent surface which differs only in it not having been plasma treated as described.
• Said orthopaedic implant may have a first surface area which represents the entire surface area of the implant.
• a first surface area which represents the entire surface area of the implant.
• At least 40%, of said first surface area may be plasma treated.
• only a back side of the implant which contacts the cement in use is treated.
• Said first surface area may be at least 3500mm 2 .
• Said first surface may be less than to 25000mm 2 .
• Said surface arranged to contact bone may have an Ra in at least one region thereof of at least 5 ⁇ , preferably at least 10 ⁇ , more preferably at least 100 ⁇ .
• Said Ra preferably extends across at least 50% or at least 80% of the area of said surface.
• Said Ra may extend across at least 20%, suitably at least 50%, preferably at least 70% of said first surface area described.
• Said orthopaedic implant suitably includes at least 50 wt%, preferably at least 75 wt%, more preferably at least 85 wt%, especially at least 95 wt% of said polymeric material. In the most preferred embodiment, said orthopaedic implant comprises at least 99 wt% of said polymeric material.
• Said orthopaedic implant is preferably arranged to cooperate with a bone associated with a joint, for example a hip, knee, shoulder, elbow, wrist or ankle.
• said implant is arranged to cooperate with a femur.
• Said implant may comprise a femoral stem, for a hip arthroplasty or may comprise a knee component for a knee arthroplasty.
• Said orthopaedic implant may be arranged to cooperate with a socket, opening or recess defined in or by a bone.
• Said implant for example said femoral stem or knee component, may be arranged to cooperate with a second orthopaedic member thereby to define an assembly for use in arthroplasty, for example in hip or knee arthroplasty.
• said orthopaedic implant of the first aspect may be a component of an assembly or arrangement (e.g. comprising a selected orthopaedic implant and a selected second orthopaedic member, wherein the implant and member are arranged to be assembled together).
• Said assembly or arrangement as described may include said orthopaedic implant and said second orthopaedic member.
• Said second orthopaedic member may comprise a metal, ceramic or polymeric material.
• Said second orthopaedic member preferably comprises a polymeric material.
• Said second orthopaedic member may comprise a polyolefin.
• Said second orthopaedic member may comprise a polyethylene, a polyurethane, a polyacetal or a polyamide.
• said second orthopaedic member comprises a polyolefin, for example a polyethylene such as UHMWPE. It may comprise a cross-linked UHMWPE.
• Said second orthopaedic member suitably includes at least 50 wt%, preferably at least 75 wt%, more preferably at least 85 wt%, especially at least 95 wt% of said polymeric material as described.
• said second orthopaedic member comprises at least 99 wt% of said polymeric material.
• part of said second orthopaedic member may be plasma treated as described herein.
• the invention extends, in a second aspect, to an arrangement comprising:
• an orthopaedic implant as described in the first aspect (i) an orthopaedic implant as described in the first aspect; (i) a second orthopaedic member arranged to be assembled with the orthopaedic implant to define an orthopaedic assembly for arthroplasty, for example, hip, knee, shoulder, elbow, wrist or ankle arthroplasty.
• the implant described in (i) and the member described in (ii) may be spaced apart in the arrangement by a distance of less than 5m, for example less than 1 m.
• the arrangement of the second aspect may also comprise a cement or one or more precursors arranged to form such a cement, for securing the orthopaedic implant to a bone.
• the cement (or at least one precursor thereof) is suitably acrylic-based.
• Said one or more precursors is suitably arranged to define an acrylic-based cement, for example an acrylate cement, preferably a polymeric cement.
• Said precursor may be arranged to define a polyacrylate cement, for example a polymethylmethacrylate (PMMA) cement.
• said arrangement of the second aspect may comprise a polyacrylate, for example a PMMA cement or one or more precursors arranged to produce such a cement.
• the cement or said one or more precursors may, in the arrangement, be spaced from the orthopaedic implant described in (i) by a distance of less than 5m, for example less than 1 m.
• the invention extends, in a third aspect, to an assembly comprising:
• the orthopaedic implant is suitably associated with, for example secured in position, by a cement which is suitably acrylic-based.
• Said cement may be an acrylate cement.
• Said cement is preferably a polymeric cement.
• Said cement is preferably a poyacrylate cement, for example a PMMA cement.
• said cement preferably contacts said plasma treated surface of said orthopaedic implant.
• the only surface of said orthopaedic implant which said cement contacts is a surface of said orthopaedic implant which is a plasma treated surface.
• said cement preferably does not contact a surface of said orthopaedic implant which is not a plasma treated surface.
• the cement (or at least one precursor thereof) is suitably acrylic-based.
• Said one or more precursors is suitably arranged to define an acrylic-based cement, for example an acrylate cement, preferably a polymeric cement.
• Said precursor may be arranged to define a polyacrylate cement, for example a polymethylmethacrylate (PMMA) cement.
• PMMA polymethylmethacrylate
• the method may comprise a step (c) which comprises selecting a second orthopaedic member (suitably being as described in the preceding aspects) which is arranged to cooperate with said orthopaedic implant referred to in (a) to define an assembly for use in arthroplasty, for example in hip, knee, shoulder, elbow, wrist or ankle arthroplasty. Steps (a), (b) and/or (c) may be in any order.
• the method may include a step (d) which comprises selecting a tool for treating a bone to define a surface to which said orthopaedic implant referred to in (a) can be secured.
• said method may comprise selecting a tool for defining a socket in a bone in which said orthopaedic implant may be secured.
• a method of securing an orthopaedic implant ton a bone of a human or animal body comprising:
• Said cement is preferably a polymeric cement.
• Said cement is preferably a polyacrylate cement, for example a PMMA cement.
• the method suitably comprises positioning the orthopaedic implant relative to the bone so said plasma treated surface is contacted with said cement in step (B).
• the method may comprise positioning the orthopaedic implant in a socket, for example defined in a femur, so that said plasma treated surface is within the socket and is contacted with said cement in step (B).
• the method may comprise selecting a precursor of said cement and causing said precursor to react to define said cement in situ.
• a combination comprising: (I) an orthopaedic implant as described in the first aspect; and
• said combination being for use in arthroplasty, for example in hip, knee, shoulder, elbow, wrist or ankle arthroplasty
• the combination may be for securing the orthopaedic implant to a bone of the human or animal body.
• the combination is for positioning in a socket of a bone (for example the femur), wherein said implant extends within said socket and said cement is arranged to cement the implant in position in said socket, suitably so the implant is substantially immovably arranged within said socket.
• implants and/or methods referred to in any aspect herein are preferably for use in arthroplasties, for example hip, knee, shoulder, elbow, wrist or ankle arthroplasties.
• Preferred treatments herein are of the human body.
• Figure 1 is a perspective view of part of an apparatus used to prepare samples for assessment
• Figure 2 is a representation of a lap-joint.
• PEEK-OPTIMA Trade Mark
• PEEK-OPTIMA Trade Mark
• PEEK grade LTI polyetheretherketone
• Example 1 describes a general method of preparing a substrate; example 2 describes how substrates may be plasma treated; examples 3 to 20 describe specific samples; examples 21 and 22 describe how samples may be prepared and tested.
• PEEK-OPTIMA substrates in the form of plates having dimensions 6 mm x 25 mm x 60 mm were prepared by injection moulding PEEK using standard conditions. In some cases, smooth PEEK-OPTIMA substrates were prepared; in other cases the PEEK-OPTIMA substrates were post-treated (e.g. by grit-blasting) to increase surface roughness (Ra).
• Substrates were plasma treated using a commercially available Nano series plasma surface machine by Diener Electronics (Germany) having the following features:
• Plasma generator power used 100%.
• Plasma generator type Radio frequency signal of 40kHz.
• Plasma treatment time 30 minutes.
• the Ra surface roughness value of samples was measured using a TALYSURF (Trade Mark) contact surface profilometer, with a standard diamond stylus, following IS04288-1996. In each case, six measurements were taken across each sample in the direction of the tensile force to be applied during shear testing.
• TALYSURF Trade Mark
• a cementing mould assembly 20, shown in Figure 1 includes a mould part 22, which includes five rectangular openings 24 in which samples 2, shown in Figure 2, are prepared. To prepare samples for testing, the assembly 20 is set up with 25mm x 25mm areas 28 of each sample exposed. Cement was mixed in accordance with the manufacturer's instructions. Then, using a powder- free gloved hand, cement was finger packed into each mould, ensuring each mould was fully filled. Then a polyethylene spacer sheet was positioned to cover the samples, a lid applied and G-clamps applied. The cement was accordingly cured under pressure in accordance with the manufacturer's instructions. After the appropriate time, the mould was disassembled and samples pressed out by hand. Samples were stored and conditioned for three days prior to testing as described in Example 22.
• Shear interface strength was calculated from the following equation.

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• Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Medicinal Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Epidemiology (AREA)
• Veterinary Medicine (AREA)
• Animal Behavior & Ethology (AREA)
• Dermatology (AREA)
• Public Health (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Prostheses (AREA)

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• 2015
  • 2015-12-16 EP EP15813530.1A patent/EP3233145A1/de not_active Withdrawn
  • 2015-12-16 US US15/536,436 patent/US20180021476A1/en not_active Abandoned
  • 2015-12-16 WO PCT/GB2015/054025 patent/WO2016097721A1/en not_active Ceased

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